1. Field of the Invention
The present invention relates to a nitride semiconductor laser element, and more particularly relates to a nitride semiconductor laser element having a protective film of a specific structure on a cavity end face.
2. Background Information
With a nitride semiconductor laser element, end faces of the cavity formed by RIE (reactive ion etching) or cleavage has narrow bandgap energy, so absorption of the exiting light occurs at the end face, this absorption generates heat at the end face, and problems such as a short service life are encountered in trying to obtain a high-output laser. Consequently, there has been proposed, for example, a method for manufacturing a high-output semiconductor laser in which a silicon oxide or nitride film is formed as a protective film on the cavity end face (see, for example, Japanese Laid-Open Patent Application H10-70338). This protective film functions as a window layer, and suppresses the absorption of light at the cavity end face.
However, with a nitride semiconductor laser element, even if the protective film is made from a material capable of suppressing the absorption of light at the cavity end face, there will still be a problem in that the desired function cannot be achieved because the protective film separates or cracks develop in the laminated nitride semiconductor layers due to a difference in the lattice constants of the nitride semiconductors.